(1) Field of the Invention
The present invention relates generally to image enhancement systems and more specifically to an array augmented parallax image enhancement system and method wherein an array of cameras with different parallax are utilized to produce a plurality of raw video streams that are combined to reduce obscurants in an output video stream.
(2) Description of the Prior Art
Under certain situations, visibility is limited by various obscurants. For example, with underwater debris and driving during snow, use of active illumination can create a field of obscuring bright images (detritus or snowflakes) whose collective flow interferes with image processing. In other applications, such as back-lit scenarios, the near-field obscurants are normally darker than the far-field object images.
Optical systems for human and automated target recognition, also known as ATR, can waste processing time and resources on unimportant foreground object patterns. The critical maximum obscurant density depends on conditions and equipment.
Several prior inventions discussed below have been developed to reduce image obscuration due to background lighting changes and electronic noise in the television camera industry. These inventions utilize both spatial and temporal methods to filter and otherwise constrain unwanted effects from becoming part of the final image stream.
Using a simple large aperture for a close focus gives a tiny depth of field but useful blurring of near-field detritus spots, which then may be perceived as non-existent. However, this technique is sensitive to the focus of the aperture. The large aperture idea may also be too cumbersome for applications such as undersea autonomous vehicles. Importantly, the large aperture technique does not use automated features of image point selection found in industrial registration software such as in shader functions. A large aperture performs only a uniform average of imaged data related to the obscuration percentage and does not utilize operator or computed input for variability of weighting of imagery from different ranges that image registration functions can automatically provide. Other inventions discussed below use a single aperture or image formed from a single lens, without the use of modern-day image registration techniques used in industry such as the virtual image sphere.
U.S. Pat. No. 4,953,032 by Suzaki et al., August 1990, discloses a motion information signal generating circuit comprising a motion detecting circuit for detecting a piece of motion information from a digitized television signal, a temporal-spatial signal processing circuit for expanding a signal representing the detected motion information both in time and space and a noise eliminator circuit connected between the motion detecting circuit and the temporal-spatial signal processing circuit. The noise eliminator circuit has at least one memory to detect the correlation between the motion information signals pertaining to two adjacent picture elements which are one horizontal sweep line part, and for instance, the motion information signal of a smaller data quantity is selected, thereby preventing appearance of a false motion signal which would be caused by a noise of increased amplitude.
U.S. Pat. No. 5,303,051 by Lévesque et al., April 1994, discloses a method of video processing that consists or obtaining a number of images of a scene and replacing missing elements of the scene, which elements are ones obscured by particles, with corresponding elements of the scene obtained from previous or following images in which those particular elements of the scene are visible. In this manner, a reconstructed image of the scene can be obtained in which the effects of the particles on the image is reduced.
U.S. Pat. No. 5,075,778 by Saito et al., December 1991, discloses a television camera with automatic lens opening control that provides pictures from backlighted scenes which neither overly darken the subject nor overly brighten the background. The lens opening is controlled by the average value of the incident light intensity, but not before the incident light intensity is subjected to a white compression process. The signal corresponding to the incident light is processed by a white compression circuit to compress the brighter portions of the signal. The compressed output is averaged and used to control the lens opening.
U.S. Pat. No. 4,275,418 by Trump et al., June 1981, discloses a video noise reduction system for incoming video information from a plurality of picture points. A first processor is capable of synthesizing each picture point from incoming picture point information from adjacent picture points to provide noise reduced picture information. A store is provided for storing picture information from at least one frame and a second processor is capable of synthesizing each picture point from incoming and stored information from a corresponding picture point from current and earlier frames to effect noise reduction. A detector is provided to detect any movement between pictures to allow processing by the first processor when movement is occurring and from the second processor when no movement is occurring. A third processor may be provided to allow synthesizing from adjacent picture points from current and earlier pictures to effect noise reduction when the picture content is detected to be stationary and has only low frequency components therein.
U.S. Pat. No. 5,019,908 by Su et al., May 1991, discloses an apparatus and method for reducing flickering in a still video frame in a digital image processing system. In a digital image processing system, an A/D converter digitizes an input analog two-field (i.e. 525 lines NTSC) video signal into first and second digital video field data components of a digital video frame, and the data of the first and second fields is stored in an image memory. Under control command, the first digital video field data is read out of the image memory, switched to a data output and D/A converted into a first analog video field for supplying the first field component of an analog video still frame, and simultaneously the first digital video field data is also stored in a field memory. The second digital video field data is then read-out of the image memory into one input of an adder while the first digital video field data is read-out of the field memory into another input of the adder, whereby the first and second digital field data is digitally summed, then passed through a divider to provide the digital average of the data of the first and second digital video fields. The averaged digital video field data is then switched to the data output and D/A converted for supplying the second field component of a 2-field analog video still/freeze frame. Flicker due to relative motion occurring between the two field of the input analog video frame is reduced by one-half in the output analog video frame due to the digitally performed averaging operation, providing an improved still/freeze frame video picture.
U.S. Pat. No. 5,021,884 by Ozaki et al., June 1991, discloses a noise reducer circuit, for video signal. In a video signal noise reducer circuit, an output video signal is delayed in a frame memory, then subtracted from an input video signal, and the resultant difference signal then passed through a high pass filter. The difference signal and the filter output signal are then compared, and the signal currently having the smaller absolute amplitude is modified by an amplitude-dependent feedback factor and then subtracted from the input video signal to obtain the output video signal.
U.S. Pat. No. 4,654,583 by Ninomiya et al., March 1987, discloses a printed circuit pattern inspection system, in which the optical image of circuit patterns is transformed into an electrical signal, the signal is converted into a binary digital signal, the connectivity relationship between selected two points of a pattern in the form of a binary signal is examined, connection data representative of the connectivity relationship expressed by a pair of numbers given to the points is generated, and the connection data is compared with design data which is produced from design information and expressed in the form of a circulation list of numbers given to points in linkage relationship, whereby determination of defectiveness of patterns is made basing on the result of comparison.
U.S. Patent 4,829,382 by Hess et al., May 1989, discloses an automatic aperture control of a television camera. R, G and B outputs from the corresponding preamplifiers of a television camera are supplied to a non-additive mixer (NAM) circuit for continuous selection of the greatest of the three outputs and the selected output is continuously supplied to a set of nine electronic switches each selecting out a subdivision of the picture field (a, b . . . i). The switched outputs for each of the subfields are then provided to respective subfield measurement detectors which each produce an average value output and a peak value output. These are stored into subfield buffer units and then read out through a multiplexer and an analog to digital converter to a microprocessor. The various values are compared with corresponding past values for selecting between various measurement schemes for obtaining a camera diaphragm control signal, namely spot measurement, center-emphasized integral measurement and selective field measurement. Except when a decision for no setting change is made, the selected scheme of measurement is used to obtain a control signal from the average and dynamic range values of the several subfieid video signals.
A need exists for an improved image enhancement system and method which can more effectively counteract image obscuration. Furthermore, a need exists for a system that takes advantage of industrial image registration capability that has been developed mostly within the past decade. Accordingly, those of skill in the art will appreciate the present invention which addresses the above discussed and other issues.